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CALIFA third data release of spectral data cubes

Bodo Ziegler, João Alves and their teams proudly present data on 667 nearby galaxies

The Calar Alto Legacy Integral Field Area Survey (CALIFA) has released to the world public all of the data assembled over 6 years of work. The data of 667 galaxies comprising more than 1.5 million spectra are freely accessible at califa.caha.es/DR3 . The astronomical community thus obtains free access to the largest dataset of spatially resolved properties of galaxies ever obtained.

Prof. Bodo Ziegler, Department of Astrophysics, has been a member of the CALIFA collaboration since his start as professor at the University of Vienna.
He actively participates in a variety of studies leading so far to 21 papers in main astronomical journals as co-author out of 41 papers published up to date from the CALIFA team. His main interests focus on kinematics, stellar populations, and star formation processes in galaxies. His team of postdocs, PhD- and master students not only works with the optical 3D-spectroscopy provided by CALIFA but Vienna is also leading the follow-up campaigns with radio telescopes of the target galaxies. “For a full understanding of the physical processes driving star formation on Galactic scales we need to combine the hot and cold Universe” says Ziegler. “The cold molecular gas measured mainly by the abundance of CO with radio interferometers is the fuel for star formation that we investigate with the optical light from stars and ionized warm gas from CALIFA.”

Also Prof. João Alves from Vienna has participated in CALIFA from its beginning in 2010, when he still was director of the Calar Alto Observatory (CAHA) near Almeria in Spain. The 3.5m telescope with the PPAK/PMAS IFU spectrograph was used in more than 300 nights over four years to conduct the survey. Alves and his team connects the galaxy-wide parameters with the local phenomena of star formation probed on small spatial scales.

The public release of all CALIFA spectral cubes and related data products is accompanied by a scientific paper describing the data acquisition, reduction processes, and quality control to be published in A&A and is available as free preprint at: https://arxiv.org/abs/1604.02289

The CALIFA third data release: an inspiration to be curious about the universe

The Calar Alto Legacy Integral Field Area Survey (CALIFA) has released to the world public all of the data assembled over 6 years of work. The data of more than 600 galaxies are accessible for anyone interested at califa.caha.es/DR3 . The astronomical community thus obtains free access to the largest dataset of spatially resolved properties of galaxies ever obtained.

CALIFA provides a unique way to learn about the evolution of galaxies. While we ourselves live in a specific galaxy, the Milky Way, there are many more galaxies out there, siblings of our own. A favorite analogy of the project Principal Investigator, Dr. Sebastian Sanchez (UNAM, Mexiko): “A social scientist would naturally learn much more about a specific human by studying her environment, her family and other social relations. Exactly in the same way can we, astronomers, support the understanding of our cosmic home, the Milky Way, by studying her siblings in the skies. Studying galaxies to learn about their evolution is a fascinating subject, because - just as humans - they come in a wide variety of appearances shaped by their specific evolutionary histories.”

Explaining in more detail the way this works, he adds: “A social scientist would like to assemble data about humans to study them, such as height, weight, number of wrinkles or favourite food. To understand human evolution in general, the social scientist would of course also like to have a group of people - a sample - that would be as diverse as possible. In the same way, with CALIFA, we collect data about galaxies that were not available before for such a diverse and complete sample of galaxies. This is because CALIFA is the first project to apply the technique of integral field spectroscopy to a sample that represents all galaxies in the Local Universe, providing with a panoramic view of galaxy evolution.”

Integral field spectroscopy is a technique that allows to determine the properties of galaxies at many different places of each galaxy, i.e. in a spatially resolved way. The CALIFA sample on the other hand has been specifically selected to be representative of galaxies in the Local Universe. This is illustrated in the figure joined to this press release, which shows how galaxy properties vary systematically with their stellar mass (i.e. the number of stars they contain) and the star formation rate (i.e. the number of stars they are newly making every year at the present time). “We knew that some galaxy properties change systematically in this diagram. But seeing this in such detail and for many properties for which this was previously not possible is new and exciting. It provides new avenues to study galaxies and understand why exactly they turn out to be as they are.” says Dr. Jakob Walcher (AIP, Germany), the Project Scientist of CALIFA.

Analysing the data from CALIFA is a challenge even for many professional astronomers. This is because the data are so rich in information. To be able to make the most out of the data, the project has been dedicated to data releases from the very beginning. “We believe that the data do not belong to us, but to anyone interested in using them. We are a publicly funded project and we see it as our duty to make the data available to the public. This also allows anyone interested to reproduce our results, which is a fundamental value for scientists.” adds Dr. Stefano Zibetti I(NAF Osservatorio Astrofisico di Arcetri, Italy), Quality Control responsible of CALIFA, and therefore fundamentally involved in making sure that the data meet all quality criteria and will be truly useful to the international community of scientists.

In summary, the main motivation to conduct the CALIFA project is our wish to understand our place in the universe. As phrased by Ruben Garcia-Benito (IAA, Spain), responsible for running many of the fundamental software pieces that turned observations from the telescope into ready-to-release data: "We hope that the nice images we produce can inspire even more people to be curious about the universe in general and galaxies in particular. At least for us the last 6 years have been a truly inspirational voyage, which we hope to continue by fully exploiting the available data in the years to come.”



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